In a treatment using a charged particle beam, by using a characteristic of the charged particle beam in which energy centrality due to a Bragg peak is very high, a Bragg peak in which a width of the charged particle beam is spread to size of a field of irradiation is formed and is uniformly irradiated to a focus of disease, so that only an affected part can be efficiently irradiated.
On the other hand, a charged particle beam may be very narrowly focused by using a magnetic field or an electric field, and by using the focused charged particle beam, a beam may be precisely irradiated on a small region and the energy can be locally concentrated. As a technique of narrowly focusing a beam, a microbeam forming technique and a pencil beam forming technique is developed. By using these techniques in particle beam treatment, a technique for treatments of a small lesion, i.e., an ion micro surgery treatment technique or the like is theoretically possible. However, since a technique for aiming a deep irradiation position with a high precision and a technique for precisely confirming, in real time, a position which is irradiated for treatment, i.e., a position where a beam reaches are not present, the ion micro surgery treatment technique is not yet realized up to now.
An eyeground observing method using a conventional eyeground observation and diagnosis device employs a method of irradiating an eyeground using eyeground excitation light, intravenously injecting an eyeground fluorescence contrast agent into a patient as needed, and observing the fluorescence from the eyeground of a subject's eye. As the eyeground excitation light source, a visible light source for observing an eyeground and an eyeground blood vessel at a retina side of a cell than the retinal pigment epithelium and a near infrared light source for observing as well an eyeground blood vessel on a choroid side of the cell of the retinal pigment epithelium are used.
When the method is combined with a device which irradiates a charged particle beam on a small lesion such as an affected part of an eye and detects a generated signal, charged particles must be often deflected from a geometric arrangement. However, a very large deflecting electromagnet is required to deflect the charged particles, and the charged particle beam may not be easily deflected in the small area.
As conventional techniques related to the present invention, techniques disclosed in Patent Document 1 and Patent Document 2 are known.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2000-237168    Patent Document 2: JP-A No. 2002-034919